linux-kernel - Re: Sysctl syscall

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Date:	Fri, 17 Nov 2006 11:38:33 +0200
From:	Hasso Tepper <hasso@...pak.ee>
To:	Andi Kleen <ak@...e.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Sysctl syscall

Andi Kleen wrote:
> On Friday 17 November 2006 09:07, Hasso Tepper wrote:
> > I have process which drops root privileges after startup and retains
> > only some privileges using CAP_NET_ADMIN and CAP_SYS_ADMIN
> > capabilities. I can change values in /proc/sys/net/ipv[46]/* (like
> > turning forwarding on/off) from this process using sysctl syscall,
> > but I can't write directly into /proc/sys/net/ipv[46]/* from it.
>
> That sounds more like a security bug than a feature to be preserved.

Why? IMHO it's normal that process with CAP_NET_ADMIN capabilities can 
modify settings in /proc/sys/net/. From /usr/include/sys/capability.h:

/* Allow interface configuration */
/* Allow administration of IP firewall, masquerading and accounting */
/* Allow setting debug option on sockets */
/* Allow modification of routing tables */
/* Allow setting arbitrary process / process group ownership on
   sockets */
/* Allow binding to any address for transparent proxying */
/* Allow setting TOS (type of service) */
/* Allow setting promiscuous mode */
/* Allow clearing driver statistics */
/* Allow multicasting */
/* Allow read/write of device-specific registers */
/* Allow activation of ATM control sockets */

#define CAP_NET_ADMIN        12


regards,

-- 
Hasso Tepper
Elion Enterprises Ltd. [AS3249]
Data Communication Network Administrator
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